H. von Specht

Comparison of the TEMPO+ ear-level speech processor and the cis pro+ body-worn processor in adult MED-EL cochlear implant users.

A study was conducted to compare the new MED-EL TEMPO+ ear-level speech processor with the CIS PRO+ body-worn processor in the COMBI 40/COMBI 40+ implant system. Speech tests were performed in 46 experienced subjects in two test sessions approximately 4 weeks apart. Subjects were switched over from the CIS PRO+ to the TEMPO+ in the first session and used only the TEMPO+ in the time between the two sessions. Speech tests included monosyllabic word tests and sentence tests via the telephone. An adaptive noise method was used to adjust each subject’s scores to approximately 50%. Additionally, subjects had to complete a questionnaire based on their 4 weeks of experience with the TEMPO+. The speech test results showed a statistically significant improvement in the monosyllabic word scores with the TEMPO+. In addition, in the second session, subjects showed a significant improvement when using the telephone with the TEMPO+, indicating some learning in this task. In the questionnaire, the vast majority of subjects found that the TEMPO+ allows equal or better speech understanding and rated the sound quality of the TEMPO+ higher. All these objective and subjective results indicate the superiority of the TEMPO+ and are mainly attributed to a new coding strategy called CIS+ and its implementation in the TEMPO+. In other words, based on the results of this study, it appears that after switching over from the CIS PRO+ to the TEMPO+, subjects are able to maintain or even improve their own speech understanding capability.

Amplitude Modulation Following Responses (AMFR) in der audiologischen Diagnostik

ZusammenfassungDerzeit ist die Registrierung von Hirnstammpotenzialen die am weitesten verbreitete Methode zur Bestimmung der Hörschwelle im Rahmen der objektiven audiologischen Diagnostik. Dieses Verfahren ist jedoch mit einer Reihe methodischer Probleme verbunden: mangelnde Frequenzspezifität bei einer breitbandigen Stimulation, geringe Aussagekraft im tieffrequenten Bereich und hohe Subjektivität der Auswertung.Eine Lösung könnte die Registrierung von Amplitude Modulation Following Responses (AMFR) darstellen. Mit ihrer hohen Frequenzspezifität aufgrund ihrer sehr schmalbandigen Stimulation lassen sie Aussagen bis in den niederfrequenten Bereich des Hörens zu.Einen weiteren Vorteil stellt der objektive Nachweis dieser Potenziale auf Basis etablierter statistischer Verfahren dar.Umfangreiche Untersuchungen zum Einfluss der Stimulationsparameter und der Ableitbedingungen haben gezeigt, dass die Registrierung von AMFR als audiologisches Werkzeug erfolgversprechend ist. Im Vordergrund standen bisher Fragen nach der optimalen Modulationsfrequenz, dem Einfluss der Vigilanz auf die Potenzialausbildung und der Nutzung bei der objektiven Bestimmung der Hörschwelle.AbstractThe registration of brainstem potentials currently represents one of the most common methods in objective audiological diagnostics. However, regardless of their use, they are still known to possess important disadvantages, such as low specificity and validity in the lower frequency range due to broadband stimuli, or uncertainties due to the need for subjective evaluation.One potential solution to these problems could involve the registration of amplitude modulation following responses (AMFR).These potentials are being discussed much more regularly within the anglo-american literature due to their known frequencyspecificity within the high frequency range (resulting from a very narrow frequencyband of stimulation), and also their ability to permit assessment of the hearing threshold at lower frequencies.Another additional advantage of AMFR results from the simple statistical verification of its presence.Extensive studies on the influence of both stimulating and recording parameters have also shown that the registration of AMFR could prove to be a very promising audiological tool, with past interest being focussed primarily on the optimal modulation frequency, the influence of vigilance of the generation of potentials, and the precise assessment of an objective threshold.

Speech Understanding with the CIS and the n-of-m Strategy in the MED-EL COMBI 40+ System

Speech tests have been performed on 6 subjects for comparing the standard 12-channel continuous interleaved sampling (CIS) strategy (CIS12), the 7-channel CIS strategy (CIS7) and the 7-of-12 strategy in the MED-EL COMBI 40+ system. An ABAB experimental design was used whereby each strategy was reversed and replicated. Speech tests were performed in quiet (vowels, consonants, monosyllables, sentences) and noise (sentences). Results showed that for vowels, CIS12 is significantly superior to CIS7, for consonants and sentences CIS12, CIS7 and 7-of-12 performed equally well, and that for monosyllables 7-of-12 is significantly superior to both CIS12 and CIS7. In addition, 7-of-12 is superior to CIS7 by almost the same amount as CIS12, but in this case the difference is not significant. Further, all strategies have been found to be equally robust in noise with respect to sentence understanding. The differences between CIS12 and 7-of-12 on the one hand and CIS7 on the other hand may be attributed to decreased spectral resolution of the latter. The fact that – in contrast to what has been reported for the SPEAK strategy – 7-of-12 is equally robust in noise as the CIS strategies is explained by the use of higher stimulation rates, wider frequency bands and a higher percentage of channels stimulated in each cycle.

Zur Abhängigkeit der amplitude modulation following response von der Vigilanz

ZusammenfassungHintergrund und Fragestellung. Die “amplitude modulation following responses” (AMFR) erlauben aufgrund der schmalbandigen Anregung der Kochlea eine gute Einschätzung des Verlaufs der Hörschwelle. Eine diagnostische Nutzung der AMFR setzt aber die Kenntnis der Abhängigkeit dieser Potentiale vom Vigilanzniveau des Untersuchten voraus.In den vereinzelten Untersuchungen, die sich in der Literatur zu dieser Problematik finden, wurde qualitativ die Amplitude der AMFR von wachen mit der Amplitude von schlafenden Probanden verglichen. Eine quantitative Bestimmung des Vigilanzniveaus durch die Registrierung physiologischer Parameter erfolgte nicht. Im Rahmen der vorliegenden Arbeit sollte die für die klinische Anwendung der AMFR wichtige Abhängigkeit der AMFR-Amplitude vom Vigilanzniveau des Untersuchten bestimmt werden. Patienten und Methodik. Dazu wurde an 8 erwachsenen Normalpersonen die Korrelation zwischen der Amplitude der AMFR und der EEG-Amplitude im Delta- und im Theta-Band bestimmt, da diese Frequenzen besonders durch das Vigilanzniveau beeinflusst werden. Als Stimulus diente ein 1-kHz-Sinuston, dessen Amplitude mit 40 Hz oder 80 Hz sinusförmig moduliert wurde. Die Untersuchungen erfolgten an den gleichen Probanden im natürlichen Schlaf und nach Gabe von Diazepam. Ergebnisse. Sowohl im natürlichen Schlaf als auch nach Gabe von Diazepam zeigte sich bei 40 Hz Modulationsfrequenz ein deutlicher Zusammenhang zwischen der AMFR-Amplitude und der Amplitude des EEG. Eine gesteigerte EEG-Amplitude bewirkte eine signifikante Verringerung der AMFR-Amplitude. Dagegen konnte bei 80 Hz Modulationsfrequenz keine Abhängigkeit der AMFR-Amplitude von der EEG-Amplitude nachgewiesen werden. Unter allen Untersuchungsbedingungen zeigten die mit 80 Hz Modulationsfrequenz ausgelösten Potentiale eine geringere Amplitude als bei Stimulation mit 40 Hz. Schlussfolgerungen. Die Ergebnisse der vorliegenden Studie legen nahe, dass bei der audiologischen Nutzung der 40-Hz-AMFR an Erwachsenen für ein konstant hohes Vigilanzniveau zu sorgen ist. Obwohl die 80-Hz-AMFR sich als unabhängig von der Vigilanz erwiesen, spricht ihre deutlich geringere Amplitude gegen eine audiologische Nutzung an Erwachsenen.AbstractBackground and objective. Amplitude modulation following responses (AMFR) allows good estimation of the hearing threshold due to the very narrow band excitation of the cochlea. Audiological use of AMFR requires knowledge of the relationship of these responses to the state of vigilance. The few studies published compared only qualitatively the amplitude of AMFR recorded in awake subjects to that recorded in sleeping subjects. A quantitative determination of the level of vigilance on the basis of recorded physiological parameters has not yet been carried out. In the present study, the relationship between the amplitude of AMFR and the level of vigilance was investigated quantitatively. Patients/methods. In eight adults with normal hearing, the relationship between the AMFR amplitude and EEG amplitude in the delta- and theta-band was determined. The amplitude in both frequency bands was used to indicate the state of vigilance. The subjects were studied during natural and drug-induced sleep. A 1-kHz carrier tone with a sinusoidally modulated amplitude of 40 Hz or 80 Hz was used as stimulus. Results. At 40-Hz modulation frequency, the AMFR amplitude correlates with the EEG amplitude both in natural and drug-induced sleep. An increase in EEG activity is paralleled by a significant reduction of AMFR amplitude. At 80-Hz modulation frequency, no relationship between AMFR amplitude and EEG activity could be detected. Under all conditions, the amplitudes of AMFR evoked by a modulation frequency of 80 Hz were significantly lower than those evoked by 40 Hz. Conclusions. These results suggest that for an audiological use of the 40-Hz AMFR the state of vigilance should be stabilised at a constantly high level. In spite of the lower influence of vigilance on the 80-Hz AMFR, this response appears less ideal for threshold estimation in adults due to the significantly smaller amplitudes.

Abschätzung der Hörschwelle mit stationären auditorischen evozierten Potentialen: Probleme der digitalen Signalverarbeitung

Zusammenfassung Die objektive Bestimmung des Horvermogens mit stationaren auditorischen evozierten Potentialen (AEP) erfordert die Einhaltung grundlegender Prinzipien der digitalen Signalverarbeitung. In der vorliegenden Arbeit werden die wesentlichen Unterschiede bei der Registrierung transienter und stationarer AEP dargestellt und daraus Bedingungen fur eine optimale Registrierung stationarer AEP im Frequenzbereich abgeleitet. Rohdaten von 40-Hz-Click-AEP und 40-Hz-AMER (Amplitude Modulation Following Response) an 5 bzw. 11 normalhorenden Probanden fur Stimulationspegel von 10 … 80 dB (nHL) wurden offline ausgewertet. Fur einen Frequenzbereich von 30 … 50 Hz wurde die Reststorung als Funktion der analysierten Periodenzahl berechnet. Es konnte gezeigt werden, das dieser schmalbandige Schatzwert der Reststorung unempfindlich gegen tieffrequente EEG-Anteile ist. Fur Meszeiten von 100 s wurden Amplituden und SNR-Schatzwerte als Funktion des Stimulationspegels berechnet.

Diskrimination musikalischer Tonhöhen bei Patienten mit Kochleaimplantat

BACKGROUND Numerous people with cochlear implants (CI) report difficulties in listening to music even though they understand speech quite well. One reason for this is a limited perception of pitch and timbre. In this study ability of adult CI subjects to discriminate musical pitch is investigated. PATIENTS AND METHODS In two psychoacoustic experiments, each conducted in 10 adult CI subjects provided with MED-EL Combi 40+ cochlear implant devices and a control group of subjects with normal hearing, individual discrimination abilities for musical pitch perception were determined. To investigate the influence of the group of instruments on discrimination ability, stimuli representing four different groups of instruments were used: woodwind (clarinet), brass (trumpet), strings (violin) and keyboard instruments (piano). RESULTS The discrimination thresholds determined varied between individual CI subjects, and on average they were significantly higher for the piano than for the other three instruments. CONCLUSIONS The results show that in subjects with CI pitch perception differs from instrument to instrument and is in general worse than in persons with normal hearing.

Überlegungen zur bilateralen CI-Versorgung

Patienten mit einer beidseitigen, an Taubheit grenzenden innenohrbedingten Hörstörung werden seit nunmehr 20 Jahren erfolgreich mit Kochleaimplantat (CI)-Systemen therapiert. Dabei erschien es aus rehabilitativen und finanziellen Gründen bisher ausreichend, die Prothese einseitig zu implantieren. Nun tritt auch die bilaterale CI-Versorgung in den Blickpunkt des Interesses. Als mögliche Vorteile einer bilateralen CI-Versorgung sind Verbesserungen der Schalllokalisation und des Sprachverständnisses im Störlärm zu erwarten. Obwohl bisher nur sehr wenige wissenschaftlich fundierte human- und tierexperimentelle Ergebnisse über den Nutzen der beidseitigen CI-Versorgung vorliegen [10], wurden Patienten beidseitig implantiert. Vor- und Nachteile der bilateralen CI-Versorgung werden seitdem sehr kontrovers diskutiert. Im Mittelpunkt der Diskussion stehen vorwiegend gesundheitspolitische Überlegungen und technische Aspekte, wohingegen dem Problem der zentralnervösen Verarbeitung wenig Aufmerksamkeit gewidmet wird.Ziel dieses Artikels ist es, die möglichen neurobiologischen und technischen Vor- und Nachteile einer bilateralen CI-Versorgung gleichermaßen zu beleuchten.

Acoustically and Electrically Evoked Auditory Brainstem Responses

In early models of the generation of the human auditory brainstem response (ABR), the successive components were considered to arise in consecutive structures of the auditory pathway (e.g. Lev and Sohmer, 1972). Waves I, II, III, IV, and V were in particular believed to originate from the 8th nerve, cochlear nuclei, superior olivary complex, lateral lemniscus and inferior colliculus, respectively. The sources of the latest ABR constituents, i.e. of Waves VI and VII, were connected to still further relays: the medial geniculate body and the acoustic radiation, respectively. Later, these early models underwent alterations (Kevanishvili, 1980; Caird and Klinke, 1984). Both neurophysiological and neurosurgical evidence was presented substantiating subcollicular or even sublemniscal origin of the main ABR complex waves including Wave V. The loci of generation of the successive components were shifted downward in proportion. Wave VI, for instance, has been stated to be related to the inferior colliculus (Hall, 1992). Recording of electrically evoked ABR in cochlear implant patients offers a unique opportunity to revise the models of ABR generation.

Diskrimination musikalischer Tonhöhen bei Patienten mit Kochleaimplantat@@@Discrimination of musical pitch with cochlear implants

BACKGROUND Numerous people with cochlear implants (CI) report difficulties in listening to music even though they understand speech quite well. One reason for this is a limited perception of pitch and timbre. In this study ability of adult CI subjects to discriminate musical pitch is investigated. PATIENTS AND METHODS In two psychoacoustic experiments, each conducted in 10 adult CI subjects provided with MED-EL Combi 40+ cochlear implant devices and a control group of subjects with normal hearing, individual discrimination abilities for musical pitch perception were determined. To investigate the influence of the group of instruments on discrimination ability, stimuli representing four different groups of instruments were used: woodwind (clarinet), brass (trumpet), strings (violin) and keyboard instruments (piano). RESULTS The discrimination thresholds determined varied between individual CI subjects, and on average they were significantly higher for the piano than for the other three instruments. CONCLUSIONS The results show that in subjects with CI pitch perception differs from instrument to instrument and is in general worse than in persons with normal hearing.